In the past, a dwelling would usually be framed on the work site employing standard structural wood members, i.e. two by four studs and two by six support members. Insulation would then be applied between the upstanding studs. Because construction grade lumber is never perfectly straight and even, problems arise when insulation of the expanded polystyrene type is applied between the studs. These must be cut to match the contour of the stud and it is an extremely time consuming process. Moreover, it is less efficient and sometimes impossible to completely insulate around curved or uneven structural members. In order to be more competitive, wall structures have been prebuilt at a lumberyard or some other place of manufacture and then transported to the site. Typically, a box frame is made with two skins, one on either side and insulation placed between. Again, such panels or structures suffer from the inability to completely insulate because of the differences in structural members. Also such structures are fairly heavy to bring to the building site.
More recently, wooden frames have been constructed and polyurethane injected therein. For instance, in Canadian Patent No. 1,176,815, entitled Structural Element for Building Purposes and Method of Making said Element, a box beam element has two spaced apart parallel surface plates and a plurality of longitudinal web plates located between the surface plates and a core of foamed plastic material fills the spaces. Upon hardening, the foam material supports the web plate so as to prevent them from tipping or tilting. The patent however, appears to be directed towards a means to support the web plates in place without nailing or gluing before the foam is pumped in.
In Canadian Patent No. 1,047,730, entitled "Building Panel Element and Method for Manufacturing Same", the frame is constructed with wooden end boards and reinforcing members similar to a standard studded frame. On the opposite side of the plate, thin wood strips are placed. The frame is then filled with foam until the foam rises to be flush with the wood strips thereby incorporating them in the foam.
In both the aforementioned patents, the panel is fairly heavy as some kind of plating or wood strip is necessary to completely contain the foam that is injected within the box. There is therefore a need to develop a lighter wall panel without heavy structural box-like members which have to be taken to the site. There is also a need to have a wall member that is completely insulated but is capable of providing anchorage for outer finishing materials such as siding, or in the case of the inside of the wall, drywall or panelling.